Various types of electronic devices have recently provided various functions due to the trend of digital convergence. For example, the smartphones not only allow voice communications but also support an Internet connection function by using a network, a music or video reproducing function, and a function of photographing pictures or videos by using image sensors.
Although the details are different for respective manufacturers or products, the electronic devices display various contents by using a display panel (screen) of a suitable size to visually support the functions. Further, the electronic devices add options for adjusting the brightness, contrast, and luminance of the screen, for convenience of the users.
In addition, there have been needs for more various luminance levels that may be set in the conventional electronic devices. Meanwhile, when the user continuously increases or decreases luminance in the corresponding setting menu to set the luminance of the screen of the electronic device, the luminance on the screen of the electronic device is neither reflected continuously nor discretely.